Luggage may typically be divided into two categories—soft luggage, and hard shell luggage. Soft luggage is typically wrapped in a soft material, such as cloth, canvas, leather, fabric, and/or vinyl. Soft luggage is typically constructed by forming an internal frame from metal and plastic materials which may be fastened together to define an interior compartment for storing items. Padding may then be applied to the exterior and interior of the plastic and metal frame, before a soft, cloth material is applied to the exterior and interior of the luggage by stitching and/or adhering it to the luggage frame and cushioning. Soft luggage is an attractive choice for luggage designers because it allows the designer to create more intricate details and aesthetic features in the soft, cloth material, which is easily cut, stitched, and arranged to create visually appealing luggage designs. However, soft luggage is typically less durable than hard shell luggage and is subject to tearing, ripping, and staining during the normal life of the luggage.
Hard shell luggage on the other hand is formed of a hard plastic material such as polyvinyl chloride (PVC), polyethylene (PE), polypropylene (PP), carbon fiber, or Tegris®. Hard shell luggage has the advantage of resisting deformation by external forces, which affords greater protection to the contents against damage as well as preserving the overall shape and appearance of the luggage. However, hard shell luggage can be heavier than soft luggage, and designers tend to have fewer options for altering the aesthetic appearance of hard shell luggage, given the typical methods of manufacturing hard shell luggage.
Hard shell luggage also typically requires a more complex manufacturing process, such as injection molding or vacuum forming. These processes include the use of expensive and complex molding equipment, multiple heating and cooling steps, trimming steps, and cleaning steps to produce the luggage body. Once the front and rear hard shell components of the luggage are formed they are typically adhered to a metal frame that is placed on the center-facing edge of the hard shells. Locks, hinges, and other hardware may then be connected to this metal frame. Liners and other internal components may also then be installed. This manufacturing process can be expensive and time consuming as compared to manufacturing processes for soft bags.
Items of luggage that attempt to combine certain features of hard and soft bags are described in U.S. Pat. No. 6,936,127 to Fenton et al. and U.S. Pat. No. 6,604,617 to Davis et al., the disclosures of which are incorporated in their entireties by reference herein. U.S. Pat. No. 8,752,683 to Scicluna also teaches a relatively simple and inexpensive manufacturing technique for forming hard shell luggage, the disclosures of which is incorporated in its entirety by reference herein. Nevertheless, there remains a need for a modular suitcase frame, the components of which may be mass produced with relatively simple and inexpensive manufacturing techniques and which components may then be adapted for various suitcase designs and assembled with less cost and labor than currently available techniques for manufacturing hard shell luggage.